Studies on T helper cells and the specificity of their soluble products for induction of cytotoxic T cells directed against trinitrophenyl-modified self

The role of T helper cells (Th) and their soluble products in the generation of a cytotoxic T-cell (CTL) response of thymocytes to trinitrophenyl (TNP)-modified syngeneic cells was investigated. The Th have a Thy 1⁺ Lyt 1⁺2^? surface phenotype, and produce at least two soluble helper factors. Production of factors requires stimulation of primed Th by specific antigen (self-TNP), and depends on a Thy 1⁺ Lyt 1⁺2^? cell. Factors present in supernatants after 5 hr of stimulation act preferentially on antiallogeneic precursor CTL (pCTL); factors present at 24 hr act preferentially on self-TNP-specific pCTL with a variable activity for alloantigen-specific pCTL. These results are interpreted as suggesting a possible role for helper factors having selective action in generation of CTL responses.